Playmobil doesn't post sales figures of individual sets or themes so there's no real way of knowing, although some people who claim to have inside information have reported that certain themes have not done well. I, for one, was surprised to read that the Roman theme did not do well and still have my doubts about this since the Egyptian theme, which is in a similar vein, came out after it and some Roman sets are still available as Add Ons. I also recall someone claiming that the dinosaur theme did poorly (I thought it would have been very successful) and yet Playmobil is releasing new dinosaur sets, which doesn't really make sense either. As for the circus theme, these sets seemed to languish on the shelves in my local Toys 'R Us and I recently saw most of the sets on clearance at Tuesday Morning.
